Regarding a resin composition for encapsulation which is used in encapsulating optical semiconductor elements such as light emitting diode (LED) and the like, its cured product is required to have transparence. In general, epoxy resin compositions obtained by using epoxy resins (e.g., bisphenol A epoxy resin, alicyclic epoxy resin and the like) and an acid anhydride as the curing agent are used widely for various purposes.
However, when the aforementioned epoxy resin composition is used as an encapsulating resin, it cannot meet the flame retardancy (UL-V-O) as the optical semiconductor encapsulating resin at the time of hardening of the epoxy resin composition. For example, an inorganic flame retarder is generally used in the prior art (e.g., see Reference 1), but there is a problem in that performance as an optical semiconductor device cannot fully be exerted due to considerable reduction of transmittance in case that the aforementioned inorganic flame retarder is added.
Reference 1: JP-A-9-100337